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Misfire with voltage drop


kevindawes

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I have come across this as has Jeff Waghorn (Bobtail84)

A bad upload can result in a "Damaged" file, with errors, sometimes the firmweare can even be corrupted ....normally as Kevin

has done here a reload of a known good file is a perm fix...sometimes relaod of the firmware might be required....

Its one of the reasons I prefer the Serial to Serial connection vs a USB convertor....ALWAYS have a known good map somewhere on you if you go tunning

I made the mistake long time ago of uploading at "Some RPM" then braked the Lappy hit the floor, just as it was uploading MSQ to the ECU....and it misfired

like a piggy all the way home as I didn't have a decent MSQ having just overwitten it :rofl:

342 BHP turned into about 30 :D .... :blush:

Best advice is

Always have a back up in case you screw it !

Serial to serial is better IMHO

Don't do at speed, tickover or stainionary better

SCREW the leads in - not just "Pushed yep sorted :blush: " <cough>

Have the MSQ on your Desktop / Laptop, NOT on a USB stick shoved in the lappy, its just another slow down of connections ....

And ENJOY now :D - congrats Kevin, whats really good is both you and Bingy had "Problems" but, even with beginners knowledge BOTH of you have sorted what were

odd and mysterious "Probs" - consider the "Fun" you could have had / have had / with a Lucas "Mystery problem" :D !

Congrats to you both !

Nige

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One thing about screwing the serial connection up, they are only supposed to hold the cable in place, do NOT do them up any more than neccessary, as you will remove the little threaded bolt thingy from your laptop... :)

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Get engine warm and post up here a data log and the MSQ File that it was logged against

I am still trying to work out how / what / why.....its serioulsy odd.....I cannot think what this could be ....hence why I would love to see a log

and see if we can see whats happening ....

Couple of things

Buy and fit new plugs - NGK BP6RES - plougs can do odd things, richness and back fires can near kill them.

When you say "It gets worse" ....is it PERFECTLY OK again if you stop, relaod original MSQ and drive back off ?

and / or what if you switch off, wait 5 - 10 mins start up and drive off again without reloading the MSQ ?

Thinking ............

Nige

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I will post a log when I next go out, although the voltage drops the same as my first post from what I saw. (I've got an issue to deal with first b4 i can post, will sms Nigel to explain)

Spark plugs are new and gapped as per your recommendation.

The map performance issue doesn't reset based on a rest, it's seems cumulative in terms of misfire as you go one regardless of stops and starts.

It was awful as I stopped for fuel, filled up, and then reloaded the map. You felt the hiccup and then it noticeable ran better at idle and off it was back in hooligan mode.

You remember when I used TS it went crazy first time out it went crazy, would this be connected?

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Tank vacuum. A possibility but never had that before and it wouldn't explain why the volts would drop. Also when I filled up with fuel the vacuum would have been released, no whoosh, and I wouldn't have only noticed the change in running once I loaded the tune at idle.

Thanks again for all your input.

Just to make sure, when I load mt, it's the first ms version in the list I choose?

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I don't think the battery volts drop is a major concern - you're going from 14.1v to 13.4v measured at the ECU connector, which is coinciding (in your screen shot) with the injector duty cycle going up to ~80%, so at that point the ECU has 80% of the max injector current flowing through its ground connection, so the small resistance in the wiring/joints will cause a greater voltage drop (voltage drop being proportional to the current).

80% duty cycle is considered about the maximum you should ever run injectors. Fuel injectors are sized to be able to supply the engine at full power without being open for more than 80% of the time, so the fact that you're somehow hitting this limit during relatively normal driving suggests some fundamental issue as that would be absolutely hosing fuel into your engine. Normally the injectors would/should not hit 80% until the engine was on the redline / under heavy load.

As an example, one of my old datalogs shows my duty cycle at 35% whilst cruising along at 2500rpm:

datalog_l2b_motorway.jpg

What's needed is to approach this methodically. 1st step is to post a datalog or two, not just a screen shot. Preferably one when you have the problem, then one after the restart fixing it.

In a non-methodical order off the top of my head:

Are you using Nige's supplied firmware & settings?

Have you changed any settings?

Can you post up your settings file?

Does stopping & restarting without touching any settings make a difference?

Does popping the fuel cap off change anything?

Does disabling the EGO correction (0% authority) change it?

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I went out today greenlaning and logged most of the day.

Here is what happened.

I'm using Nigel's tune and have only modified the idle and the controller authority from 15% to 5%.

Spent the first 6 hours running fine then I noticed a drop in power which came on gradually. I reloaded the tune with controller authority set 0 and although there was a slight improvement. Completely shut everything done and reloaded the tune and switched off completely and waited ten minutes. It then ran better but still underpowered slightly and degraded further as I drove home which was a fifty mile drive.

Looking at the logs it looks ok until the problem really is noticeable and the volts, on the log, then starts jumping about.

It's like a component starts to breakdown. Reloading the tune helps but doesnt cure it, it starts to degrade again.

In answer to fridgefreezers questions, answers below'

Are you using Nige's supplied firmware & settings? basically yes

Have you changed any settings?yes, idle speed and the authority

Can you post up your settings file? I'll try

Does stopping & restarting without touching any settings make a difference?no

Does popping the fuel cap off change anything?no

I'll load up the logs shortly

thanks in advance

Does disabling the EGO correction (0% authority) change it?no

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Best advice is

And ENJOY now :D - congrats Kevin, whats really good is both you and Bingy had "Problems" but, even with beginners knowledge BOTH of you have sorted what were

odd and mysterious "Probs" - consider the "Fun" you could have had / have had / with a Lucas "Mystery problem" :D !

Congrats to you both !

Nige

Somehow i have managed to overlook this thread.

Thanks for the vote of confidence Nige :i-m_so_happy:

Good luck in finding your problem Kevin :blink:

Sadly far too technical for me -

Maybe in 12-18 months time :rofl:

(The only settings i know are the settings tab in Megatune, top row second one in from left)

HTH

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I don't think it's anything to do with the battery voltage, but it's an unexplained symptom which might point you to the real issue.

I don't see anywhere you've actually checked to see if the voltage really is dropping, or if the MS just thinks it is?

I'd get a real meter on the battery (directly across the terminals) and drive around until the fault occurs.

Then I'd repeat it measured at the MS plug, *and* grounded at the MS plug.

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  • 2 weeks later...

Hi, back again. Was off-line due to a family issue but now that normality is returning keen to get the motor sorted, thanks again for all the help and advice.

Ok where am I now, well, Nigel kindly sent me his spare ecu that I just connected up.

Went out for a little drive and logged the results (attached)NIGEL ECU RUN 1.xls

The only thing I'd had changed was the authority to 5% and the idle down to 1000 from 1400.

It was only a shortish run but performance didn't feel like it was degrading, I'll need to run it for a few more hours to make sure though.

The log is below, the gego looks a bit on/off - is that ok?

I ran the analyser which changed a few figures which I saved but over wrote the idle rev range keeping them original. Again, is this ok - how you do it?

I still need to set my base idle and double check my timing (never seem to have enough time) but it appears to be running ok this first time out.

Fingers crossed.

Kev

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